1. Field of the Invention
The present invention relates to composite materials made using aerogel foam, and the process for the manufacture thereof. More particularly, the invention is based on the use and properties of aerogels.
Aerogels are open pore, low density solids (typically 5% solid) that are easily permeated by gases. Aerogels typically have a high surface area and can exhibit catalytic properties towards gas-phase reactions. Aerogels are made using sol-gel processing followed by supercritical extraction of the entrapped solvent. A combination of reacting fluids and solvents are mixed together and form a gel (a low density network of solids containing the solvents and liquid reaction products). To remove the solvent without destroying or altering the solid network, the gel is placed in a vessel and the temperature and pressure are raised above the critical point of the contained solvent. Thereafter the pressure is released. The resulting material is aerogel and is the starting point for this invention. Aerogels can be made of many materials including metal oxides, polymers, and carbon.
2. Description of Related Art Aerogels are known in the art. For example, aerogels have been described in U.S. Pat. No. 4,610,863 and U.S. Pat. No. 2,093,454 (S. S. Kistler, 1937); and in various articles, i.e. Aerogels, appearing in Scientific American, May 1988, Vol. 256, No. 5.
The aerogels described in the prior art are transparent arrays which can be utilized, for example, in windows, refrigerators (as insulation or as insulating windows), ovens (as insulation or as insulating windows), or in the walls and doors thereof, or as the active material in detectors for analyzing high-energy elementary particles or cosmic rays.
The uses of the aerogels of the prior art are somewhat limited, because they do not possess characteristics desirable for certain uses. For example, they are structurally weak and friable, can be broken down by water, and require vacuum-packing to attain their highest thermal-insulation properties.